BH250-47
Title
BH250-47
Subject
Gneiss
Description
Major Minerals: sillimanite, : cordierite?
Minor Minerals: biotite, muscovite, plagioclase, quartz, microcline, zircon
Optics: fibrous or fibrolitic aggregates of sillimanite
BH250-47 is from the Beartooth Mountains, which expose high-grade Archean gneisses and migmatites that record very high-temperature, high-pressure mineral assemblages. This rock hosts sillimanite- and cordierite-bearing metapelitic units and migmatites. The sillimanite occurs as fibrous to fibrolitic aggregates. his mineral pair is characteristic of pelitic (Al-rich) metasediments, such as original shales and siltstones.
Metamorphic grade — BH250-47 reached very high temperatures, corresponding to upper amphibolite to granulite facies, approaching migmatitic conditions.
Minor Minerals: biotite, muscovite, plagioclase, quartz, microcline, zircon
Optics: fibrous or fibrolitic aggregates of sillimanite
BH250-47 is from the Beartooth Mountains, which expose high-grade Archean gneisses and migmatites that record very high-temperature, high-pressure mineral assemblages. This rock hosts sillimanite- and cordierite-bearing metapelitic units and migmatites. The sillimanite occurs as fibrous to fibrolitic aggregates. his mineral pair is characteristic of pelitic (Al-rich) metasediments, such as original shales and siltstones.
Metamorphic grade — BH250-47 reached very high temperatures, corresponding to upper amphibolite to granulite facies, approaching migmatitic conditions.
Coverage
Location: Beartooth Mountains, Wyoming, USA
Nearby Geographic Feature: Beartooth Mountains
GPS Coordinates: 44°56'12.14"N, 109°37'21.49"W
Nearby Geographic Feature: Beartooth Mountains
GPS Coordinates: 44°56'12.14"N, 109°37'21.49"W
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-47. Housed at Carleton College in Minnesota.
Contributor
Bereket Haileab
Type
Thin section
Relation
Collection
Citation
Bereket Haileab, “BH250-47,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/54.